1. Field of the Invention
The present invention relates, in general, to drum washing machines and, more particularly, to a drum washing machine which recovers heat during a drying-mode operation to dry clothes. The washing machine recovers heat from high temperature humid air flowing from a water tub and combines the recovered heat with low temperature dry air flowing from an area around a condensing nozzle, thus saving time and energy during the drying-mode operation.
2. Description of the Related Art
In conventional drum washing machines, a rotary tub is horizontally arranged in a cabinet so as to rotate clockwise and counterclockwise around a horizontal axis of the cabinet to repeatedly move clothes seated on an internal lower surface of the rotary tub along with wash water in an upward direction and allowing the clothes to be dropped due to gravity from a top to a bottom of the rotary tub, thus washing the clothes.
In the drum washing machines, the rotary tub is set in a water tub containing wash water therein, and rotates in the water tub by a drive motor. A door is mounted by a hinge to a front of the water tub, thus allowing a user to put the clothes into and take the clothes out of the rotary tub before and after washing the clothes.
Some models of the conventional drum washing machines are provided with clothes-drying units to dry wet clothes after washing the clothes. The clothes-drying units include an air duct installed around an outer surface of the water tub so as to communicate with an interior of the water tub, with a blower fan and with a heater installed in the air duct. In addition, a condensing nozzle is provided in the air duct to remove moisture from high temperature humid air, flowing from the water tub after passing through the clothes seated in the rotary tub, thus forming lower temperature dry air.
When the clothes in the rotary tub are completely washed and spin-dried through a washing-mode operation and a spin-drying-mode operation by rotation of the rotary tub, a drying-mode operation to dry the clothes begins. To start the drying-mode operation of the drum washing machine, both the blower fan and the heater installed in the air duct are turned on. During the drying-mode operation, the low temperature dry air flowing from an area around the condensing nozzle passes through the heater, t becoming heated and changing into high temperature dry air. The dry air is, thereafter, introduced into the water tub wherein the high temperature dry air passes through the clothes in the rotary tub, removing moisture from the wet clothes. While the high temperature dry air passes through the clothes, the dry air is humidified, becoming high temperature humid air. The humid air flows to the area around the condensing nozzle, becoming low temperature dry air again. The above-described cycle of the clothes-drying unit is repeated for a predetermined time period until the clothes are dried to a desired level.
However, the conventional drum washing machine having the clothes-drying unit has several drawbacks, as described below. When the high temperature humid air flowing from the clothes seated in the rotary tub passes through the area around the condensing nozzle which condenses moisture of the humid air to change the humid air into dry air, the temperature of the air is substantially reduced by cold water which is sprayed from the condensing nozzle to condense the moisture of the humid air. Therefore, the conventional drum washing machine must be provided with the large capacity heater to change the low temperature dry air into high temperature dry air, thus excessively consuming electricity. Furthermore, since it is necessary to heat the air by the large capacity heater in every cycle, the time required in the drying-mode operation is undesirably increased.
Typically, the drying-mode operation of the drum washing machine is performed for a lengthy period of time even though the drying time varies in accordance with a quantity of the clothes to be dried. However, the large capacity heater must be used in the conventional drum washing machine, thereby causing excessive power consumption by the drum washing machine and forcing the user to pay excessively for consumed electricity.